Impulsing generating circuits



July 26, 1960 E. s. PETERSON 2,946,853

IMPULSING GENERATING CIRCUITS Filed Jan. 3, 1955 IN VEN TOR.

EDWARD S. PETERSON BY @QM ATTY.

United States Patent IMPULSING GENERATING CIRCUITS Edward S. Peterson, Elmwood Park, Ill., assign'or to Automatic Electric Laboratories, Inc., a corporation of Delaware Filed Jan. 3, 1955, Ser. No. 479,503

8 Claims. (Cl. 179-17) This invention relates to arrangements for identifying calling stations on multi-party lines in automatic telephone systems and, more particularly, to impulse generating circuits in such arrangements. In one arrangement heretofore -known each of the party subscribers on a multi-party line is provided with a conventional dial operated impulse transmitter in which a main impulsing cam periodically opens the line circuit to transmit a series of impulses in a well-known manner to operate an -irnpulsing relay. The line circuit is normally closed through one winding of an -electropolar relay of the type disclosed in U.S. Patent 1,673,884, the current in the line circuit and through this winding supporting the action of a second current `through a second winding of this relay which second current holds the armature of the electropolar relay in Ia first operated position. The periodic opening of the line circuit when no current ows through the said first winding will have no effect upon the second winding and the said armature will remain in its first operated position.

In the dial operated impulse transmitter is also provided an auxiliary impulsing cam co-rot-atable with the said main impulsing cam and adapted to periodically close an identification impulsing circuit in a predetermined sequential relationship with the periodic opening op the line circuit. This identification impulsing circuit is periodically closed also through the said one winding ofthe said electropolar relay, the current in the last-named identification impulsing circuit however flowing in a direction opposing the action of the current through the said second ywinding of the electropolar relay. The current in the said one winding is now effective to move the said armature to a second operated position and registering circuits controlled by the armature of ythe electropolar relay can be energized in accordance with the identification impulses generated by the auxiliary impulsing Cam.

A relay such as the one described, although operating satisfactorily, is highly critical of adjustment; any stray potential such as a stray ground potential may be instrumental in causing a current to flow through the first winding so as to cause the armature to assume its second operated position and energize the associated identification impulse registering circuits. Further, an electropolar relay is subject to the usual wear of more common relays while lacking the advantage of simplicity.

The present invention, to provide identification impulses in response to the operation of the identification impulsing cam of the dial operated impulse transmitter, substitutes in the aforementioned identification impulsing circuit the combination of a gas discharge tube 'and a simple direct acting relay. The present invention thereby achieves its primary object which is to provide an identification impulsing circuit responding to a dial operated identification cam which will be positive in operation and will 'at the same time be subject to relatively little wear.

It is another object of this invention to provide an identification impulsing circuit the components of which are economical to procure, are durable and 4will require a minimum amount of adjustment.

Other objects and the special features of this invention will become apparent from a persual of the detailed description of the invention which follows. illustrating one embodiment of the present invention is the single figure of the drawings showing in schematic form the relationship of the circuit components.

In my invention a dial operated impulse transmitting' device represented at 10 is provided with a digital impulsing cam 11 with which is operatively associated the break contacts 12. The contacts 12 are included in series with a conventional line circuit by means of the conductors 13 and 14. The loop resistance of the line circuit may be yconveniently represented by the resistances 15 and 16. Also included in the line circuit is an impulsing relay 17 having the break contacts 1S and 21 and the make contacts 19 and 20 associated therewith. The relay 17 is well-known and may be of the 400 ohm type. Completing the line circuit are a suitable source of potential 24 and a divider resistance 25 connected to a common terminal 26 and which may be conveniently connected in the circuit by means of the conductors 22 and 23, respectively. Also provided in the dial impulse transmitting device 10 is an identification impulsing cam 27 with which is operatively associated the make contacts 28. The contacts 28 are included in series with an identification impulsing circuit which may be traced from ground through a resistance 29 representing the ground resistance, the contacts 28, conductor 14, the representative resistance 16, the conductor 23, divider resistance 25, common terminal 26, through an additional source of potential 30 which may be the conventional main exchange battery, and, from the positive side of the source 30, to ground.

A gas discharge tube 40 which may be a thyratron tube of the type commercially designated as 6D4 is associated with the identification impulsing circuit. In the plate circuit of the tube 40 is connected a conventional relay 50 having associated therewith the operating contacts 51 which may be utilized to control related identiiication register circuits, not shown. The plate circuit of the tube 40 may be further traced from the relay 50 through the make contacts 20 of the relay 17 to ground, from ground to the positive side of the potential source 30 which supplies the space potential for the tube 40,

through the source 30, the common terminal 26, a non-y inductive resistance 42 and the cathode of the tube 40. The control grid of the tube 4G is connected through a protective resistance 43 and a condenser 44 to the ground or positive side of the .divider resistance 25. A transformer 45 is connected by means of its primary winding 46 to a source of alternating current and furnishes through a tertiary winding 47 a heating current to the filament of the tube 40. A center-tapped secondary winding 48 of the transformer 45 connects through its terminals to a pair of rectifying elements 49 which in turn Iare connected to a common terminal 60. The center-tap 51 is connected by means of the conductor 52 to the negative side of the divider resistance 25. Connected between the condenser 44 and the resistance 43 of the tube 40 control grid circuit on the one side and the common terminal 60 on the other side, is an isolating resistance 53. Also connected to the common terminal 60 between the pair of rectifying elements 49 and the center-tap 51 is a rectifier load resistance 54 anda capacitor 55 which capacitor comprises an input filter for the rectifier elements 49. The contacts 18 and 19 of the impulsing relay 17 may be used to control local switching circuits, not shown, as is well-known in the art.

The tube 40 is vnormally negatively biased by a direct current potential developed across the load resistance 54 by the action of the rectifier elements 49 which, together with the center-tapped winding 48, comprise a full-wave rectifier. The direct current biasing potential is maintained ata substantially steady value by the capacitancei'nput filter 55. 'Ihe negative biasing potential is applied to the control grid oftube 4t) through the isolating resistance 53 and the resistance 43 and effectively prevents the tube 40 from conducting. The tube 40 will be unaffected by the current How in the line circuit closed at the normal break contacts 12 since the direction of the ow is such that any potential developed across the dividerV resistance 25 will serve to increase the negative bias on the control grid. Nor will the periodic opening ofthe line circuit through the operation of, the digital impulsing cam 11 aect the tube 40` since any opening of the line circuit will tend toremove any potential whatever from across the divider resistance 25 and hence leave the normal negative bias of the grid unalected.

' Upon the closure of the switchhook contacts, not shown, at the substation, contacts 12 and hence the line loop, are closed and line relay 17 is energized to prepare, at its make contacts 20, the plate circuit for the tube 40 as hereinbefore described. Thus the plate circuit of the tube 40 will be prepared while dial 10 is at normal and also during the intervals between digital impulses when the contacts 12 are closed. The tube 40 cannot conduct due to the negative bias on its grid. However, the identification impulsing cam 27 is so adjusted with respect to the digital impulsing cam 11 that the contacts 28 are closed only at alternate times with the opening of the contacts 1 2, that is, are closed only Within one or more time intervals during which contacts 12 are closed. It is duringthese time intervals then, that the identification circuit hereinbefore described is completed. In the embodiment shown in the drawing, identication cam 27 closes contacts 28 twice, namely shortly before and then again shortly after the last impulse of the digit is sent by contacts 12. Generally speaking, the dial operated impulse transmitting device sends out identification pulses in a manner substantially the same as that disclosed in Figs. 1 and 2 of I. E. Ostlines United States Patent No. 2,366,647. When the first identification impulse is transmitted by contacts 28, a positive voltage appears across the divider resistance 25 via thel identification impulsing circuit previously described. This positive voltage charges the condenser 44 and is applied to the control grid of the tube 40 through the resistance 43. The latter potential is of a sufficient value to overcome the negative bias on the grid rand to raise the grid bias to the firing potential of the tube 4t). The tube 40 thereupon fires removing control of the tube 40 from its grid and a circuit, previously described, is completed through the relay 50 which, by reason of the current in the last-named circuit, operates its associated contacts 51 which in turn may operate identification registering circuits, not shown. The resistance 42 in the plate-cathode circuit of the tube 40 is provided to limit the `amount of current owing in the latter circuit.

Upon the opening of contacts 28 after the first identication impulse has been sent, control of the tube 40 can be returned to its control grid only if conduction is interrupted and the tube allowed to `de-ionize by removing its plate supply voltage. This is accomplished, as previously described, by placing the plate circuit of the tube 40 under the control of the relay 17. Thus when the line circuit is now opened by the operation of the digital impulsing cam 11 and its associated contacts 12 the relay 17 will be deenergized, and the contacts 20 allowed to open, thereby opening the tube 40-plate circuit and interrupting conduction in the tube 40. The

tube 40 completely de-ionizes during the time required for contacts 12 to transmit one impulse. VThe control grid of Vthetube V40 ,again assumes control and the identifcation impulsing circuit is ready for the second opera- .4 tion of the identification impulsing cam 27 and its associated contacts 28.

It is readily seen from the description of the operation described above that the relay 50 can be caused to operate alternately with the relay 17 or at any interval between digital pulses when the relay 17 holds the contacts 20 closed. Thus identification impulses can be generated alternately with digital impulses in any number and in any alternate relationship depending only upon the sequence of operation of the identification impulsing cam 27 `and digital impulsing cam 11. It is further obvious from the above description that modications may be made in the structure and operation without departing from the scope of the invention. By way of illustration, the negative bias for the tube 40 may equally well be obtained from the source of potential already included in the arrangement described or an additional battery to supply this bias may be provided. Further the tubeA could equally receive filament current from the said potential source or an additionally provided potential source. Other modifications may be made, also without deviating from the scope of the invention as set forth in the appendant claims.

What is claimed is:

1. In a telephone system, a substation identiiication arrangement comprising a telephone line, a substation connected to one end of said line and having a dial with a digital impulse contact and an identification contact, there being provided at the other end of said line a digital impulse responsive relay periodically operated and released under the control of said impulse contact, an electronic detecting device periodically rendered conductive under the control of said identication contact, the

Y state of conductivity of said detecting device each time vice from being thus rendered conductive, and for subsequently transmitting said state of conductivity, with said digital impulse responsive relay in unoperated condition, the termination of said state of conductivity upon release of the digital impulse responsive relay causing said identification relay to release preparatory for the next cycle of operation.

2. In a telephone system, the combination set forth in claim 1 wherein there is provided a common impedance element controlling said electronic detecting device and two sources of direct current potential, and said telephone line comprises a pair of conductors, said digital impulse responsive relay is controlled over a rst circuit including said rst source of potential and extending over said two line conductors, said identification relay is controlled, through the medium of said common impedance element and said electronic detecting device, over a second circuit including said second source of potential and extending over one of said conductors and ground, and said common impedance element is included in both said first and said second circuits.

. 3. In a telephone system, the combination as set forth in claim 2, wherein there is provided a third source of direct currentpotential and wherein said electronic detecting device comprises a gas tube, the grid of said tube being normally biased by said third source of potential to prevent conduction, said bias being overcome by a potential due-to the closure of said second circuit thereby rendering said tube conductive and causing the operation of said identification relay, said identification relay being connected in the plate circuit of said tube.

v 4. In an automatic telephone system, an automatic switching control circuit, a subscriber line having at one end a dial with first and second impulse contacts, said secondimpulse-contacts being closed only during a period or periods in which said rst impulse contacts are closed and at the other end electronic impulse detecting means andriirst and secondrrelays, two circuits extending over Said line to said first relay and said electronic detecting means respectively, said first relay being periodically energized and deenergized over said first circuit, under the control of said rst impulse contacts, to periodically close said automatic switching control circuit, said electronic detecting means being rendered conductive over said second circuit, under the control of said second impulse contacts, to cause said second relay to operate responsive thereto, and contact means controlled by said first relay to periodically render said electronic detecting means non-conductive thereby causing said second relay to release yafter each of its operations.

5. In an impulsing arrangement, a normally closed circuit including a first source of potential, a first relay, a rst contact means, operated by a dial, for periodically opening said normally closed circuit, voltage dividing means, said iirst source of potential causing a current to liow in said normally closed circuit in one direction through said voltage dividing means to energize :said first relay, said first contact means periodically opening said normally closed circuit to thereby periodically deenergize said first relay, a normally open circuit including said Voltage dividing means, a second source of potential and a second contact means, operated by said dial, for periodically closing said normally open circuit to thereby cause said second source of potential to cause a periodic current to fiow in said last-mentioned circuit in `another direction through said voltage dividing means, an electronic discharge means associated with said normally open circuit and periodically energized responsive to said periodic current through said voltage dividing means in said other direction only when said first relay is energized, a second relay associated with said electronic discharge means, said second relay periodically energized responsive to said periodic energization of said associated discharge means, and contact means associated with said first relay and operated responsive to said periodic deenergization of said first relay to periodically deenergize said discharge means to thereby periodically deenergize said second relay.

6. In an impulsing arrangement, a combination as claimed in claim in which said electronic discharge means comprises a gas discharge tube having a predetermined ionization point, said tube biased below said ionization point to prevent energization of said tube, and

aereas@ said voltage dividing means comprising a resistor, said periodic current through said resistor in said other direction periodically biasing said tube above said ionization point to thereby periodically energize said tube.

7. An impulsing arrangement comprising a normally closed circuit including a first source o potential, a first relay, a resistor and a first contact means, operated by an impulsing device, for periodically opening said normally closed circuit, said first source of potential causing a current flow in said circuit and through said resistor in one direction whereby said first relay is energized, said lirst relay periodically deenergized as said normally closed circuit is periodically opened by said first Contact means, a normally open circuit including said resistor, a second source of potential, and a second contact means operated by said impulsing device for periodically closing said normally open circuit to thereby cause said second source of potential to periodically cause a current ow in said circuit through said resistor in an opposite direction, a third circuit including a gas discharge tube having a predetermined ionization point, a second relay and a third contact means for opening said third circuit operated responsive to said deenergization of said first relay, said gas discharge tube having a control grid associated with said resistor and means biasing said tube below said predetermined ionization point to prevent energization of said tube, said periodic current flow through said resistor in said opposite direction periodically biasing said tube above said ionization point to periodically energize said tube only when said first relay is energized, to thereby periodically energize said second relay, said periodic `deenergization of said first relay operating said third contact means to periodically open said third circuit to thereby deenergize said discharge tube whereby said second relay is periodically deenergized.

8. An impulsing arrangement as claimed in claim 7 in which said normally closed circuit is open at alternate times with the closing of the normally open circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,366,647 Ostline Ian. 2, 1945 2,591,937 Herrick Apr. 8, 1952 2,708,690 Mitchell May 17, 1955 

